Does winter application of road salt affect zooplankton communities in urban ponds?

Road salt (NaCl) is commonly used as a deicer during winter to improve road safety, resulting in freshwater salinization. Such elevated chloride concentrations may have a strong effect on zooplankton, which are key elements in freshwater food webs. The aim of this study was to investigate the effect of chloride ion concentration and inter-pond environmental variability on zooplankton density in four urban ponds over 3 years differing in winter conditions. Analysis of variance showed significant differences in chloride ion concentration and zooplankton density regarding study year and ponds. Redundancy analysis of column water data showed that both the environmental variables (including chloride ion concentration) and the pond location significantly contributed to the model explaining the variability in zooplankton densities. However, the environment variable (referring to the environmental variables) had a smaller contribution (11%) than the POND variable (related to the spatial configuration of the ponds), which contributed 62%, indicating that the dynamics of zooplankton density depended primarily on ecosystem characteristics. Even so, although chloride content was not the main determinant of zooplankton density, their presence in aquatic ecosystems and potential interactions with other types of pollutants could have negative biological and ecological effects.